Injection molded plastic article with integral weatherable pigmented film surface

ABSTRACT

Molded articles having contoured, decorative outer surfaces are disclosed. The articles comprise a molded polymer substrate and a decorative surfacing film adhered to one side of the substrate. The decorative surfacing film comprises a substantially molecularly unoriented cast polymer film formed from a weatherable polymer. The articles are particularly suited for use as automobile body panels and the like. Also disclosed is a method for making such articles, and a method for making sets of such articles for assembly into automobile bodies and the like.

This application is a continuation of copending application Ser. No.07/410,662, filed Sep. 21, 1989, now abandoned, which in turn is acontinuation-in-part of Ser. No. 06/924,295 filed Oct. 28, 1986, nowabandoned.

FIELD OF THE INVENTION

This invention relates to shaped molded polymer articles generally, andparticularly relates to shaped articles formed from a molded polymersubstrate which have a decorative surfacing film on the outer surfacethereof presenting a surface appearance of high quality comparable to ahigh quality automotive paint finish.

BACKGROUND OF THE INVENTION

The trend in the automobile industry is towards increased use of plasticbody panels in automobile construction. Use of such panels makes itpossible to reduce the weight of the automobiles and also to reducetooling costs arising from body styling changes, while providingincreased styling freedom in car design. Other advantages arising fromthis type of construction include reduced facility costs and factoryfloor space requirements, and process cycle times allowing thejust-in-time, low inventory manufacturing of parts at or near theautomobile assembly plant. See C. Kirkland and P. Dickard, Dateline:Detroit. SAE Show News Bulletins, Plastic Technology, page 103 (April1986).

A significant problem with plastic automobile body parts is that many ofthe most desirable molding polymers for such parts are not weatherable.Moreover, many such polymers do not provide a good bonding surface forpaints. Even where paint bonding problems are overcome, conventionalspray-painting techniques pose a significant pollution problem arisingfrom the evaporation of noxious paint solvents, and, further, are veryexpensive if a high quality, multiple coat paint finish is to beobtained. Because the overall finished appearance of an automobile isamong its most important selling features, these problems are serious,and a great deal of effort and expense is being devoted to theirsolution. See, for example, Automotive Coatings: Helping Detroit WooConsumers, Chemical Week, page 30, (Jul. 4, 1984). One approach to thisproblem is to provide a film surface for the plastic part.

Various molded polymer automobile parts with film surfaces have beenmade in the past. For example, clear, unpigmented, nonweatherable, castPVC films have been used to surface interior automobile parts. Anotherexample, U.S. Pat. No. 3,679,510 to Conley and Ellison, discloses areverse-printed, oriented, polyvinyl fluoride film (a "TEDAR" film)bonded to a molded polymer substrate. Such weatherable, oriented filmsare excellent for use in making side rails and other automobile trimparts. These films are, however, difficult to uniformly internallypigment, and are generally not suitable for use in a deep draw moldingprocedure. In order to be useful as a surfacing film on exteriorautomobile parts, the film must duplicate the surface appearance of aquality automobile paint finish. The finish must have high gloss, highdistinctness of image (DOI), excellent weatherability and durabilityunder exposure to sunlight and temperature extremes, and the film mustmatch the solid and metallic colors used in automobile paint finishes.

Accordingly, an object of the present invention is to provide a moldedpolymer article which has a weatherable surface.

A further object of the invention is to provide an article as describedabove which has a high grade decorative finish suitable for use as anautomobile body part.

An additional object of the invention is to provide an article of thetype described which can be deep draw molded into variousthree-dimensional shapes used in automobile body parts.

SUMMARY OF THE INVENTION

These and other objects and advantages of the present invention areachieved in the embodiments illustrated herein by the provision of anarticle having a contoured, decorative outer surface, and which iscomprised of a molded polymer substrate and a decorative surfacing filmadhered to one side of the substrate and conforming to the contouredsurface. The decorative surfacing film comprises a substantiallymolecularly unoriented cast polymer film formed from a weatherablepolymer, which film has pigments, such as colored pigments or reflectiveflakes, uniformly distributed therein.

Use of a cast polymer film is important in obtaining uniformdistribution of the pigments within the film and enables the productionof a high-quality decorative surfacing film with an appearance whichclosely simulates the high grade automotive paint finishes used onautomobile body parts. Such pigmented, cast, weatherable films aresuitable for deep draw molding, as will be explained below, and do notrequire the use of separate pigment layers in addition to a protectiveweatherable outer layer.

A shaped article as described above is made by placing into a moldhaving a contoured, three-dimensional molding surface, a preformeddecorative surfacing film of the type described above. A moldablepolymer is then introduced into the mold on one side of the surfacingfilm. The surfacing film is then molded into a contouredthree-dimensional configuration conforming to the molding surface ofsaid mold, while molding said polymer to form a shaped article with thedecorative surfacing film adhered to the outer surface thereof.

The decorative surfacing film also includes a bonding layer formed of athermoplastic thermoformable polymer, different from the cast film. Thedecorative surfacing film is placed into the mold with the bonding layeroriented inwardly away from the molding surface so as to become adheredto the moldable polymer.

Also disclosed herein is a method of making a structure such as anautomobile body which has a uniform decorative outer surface, which iscomprised of a set of interconnected shaped articles, each article beingformed from a molded polymer material (and optionally from a pluralityof different moldable polymer materials), and each article having adecorative surfacing film on the outer surface thereof presenting asurface appearance of high quality comparable to a high qualityautomobile paint finish. Each article in the set is preferably formed ofa moldable polymer which is selected to provide the desired structuralproperties to the particular location in the assembled structure inwhich it is installed. At the same time, while the assembled structuremay be formed from different structural polymer materials, it has anouter surface which is uniformly colored in accordance with apredetermined color scheme (single colored, multicolored, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an apparatus and procedure formaking molded plastic articles of the present invention.

FIG. 2 is a cross-section of a decorative film, taken along the line2--2 of FIG. 1.

FIG. 3 is a perspective view of an automobile formed from a set ofmolded plastic articles of the present invention.

FIG. 4 is an exploded view of a set of molded plastic articles of thepresent invention.

FIG. 5 is a cross-section of a molded plastic article taken along theline 5--5 of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Molded plastic articles of the present invention can be made by placinga preformed decorative surfacing film 10 into a mold 11, closing themold, and injecting a moldable polymer 12 into the mold on the innerside of the film 10 (see FIG. 1). The decorative surfacing film, asshown in FIG. 2, comprises a substantially molecularly unorientedweatherable cast film 13 which has pigments uniformly distributedtherein, and a bonding layer 14 formed of a different polymer adhered tothe inner side of the cast film.

Molded plastic articles 20 of the present invention are useful in avariety of applications where it is desired to have a high qualitypaint-like appearance on a molded plastic article. Such articles areparticularly suitable for use in exterior applications such as exteriorbuilding panels or as outer body panels in an automobile, as illustratedin FIG. 3. Such an automobile has a body which is comprised of a set ofmolded plastic articles 20, as illustrated in FIG. 4. FIG. 5 illustratesa cross section of a molded plastic article of the present invention,with the preformed decorative surfacing film adhered to the moldedpolymer substrate 20. FIG. 5 shows that the bonding layer 14 is adheredto the molded polymer substrate 20, with the weatherable cast film 13 onthe outer surface of the article.

Cast films for practicing the present invention should be selected sothey are pigmentable, thermoformable and weatherable. Such films aresubstantially molecularly unoriented cast films, as opposed to filmswhich have been oriented or biaxially oriented. The films are"preformed" films, in that they are provided as self-supporting sheetsof material. Such films are prepared by a number of known liquid castingmethods, such as by spreading a solvent solution having a polymerdissolved therein onto a carrier with a casting die, doctor bar, orreverse roll coater, then evaporating the solvent, and then strippingthe polymer film from the carrier. The reverse-roll coating method isthe preferred method of making liquid cast films for the presentinvention. Other liquid casting methods are also known and useful forpracticing the present invention. In appropriate cases, a plastisol,organosol, or dispersion of the polymer can be cast onto the carrierinstead of a solvent solution. For example, polytetrafluoroethylene,which is virtually insoluble, can be cast as a dispersion. Such liquidcast film processes, and some current uses of cast films, are discussedin Plastics Engineering, at pages 29-33 (May, 1983). Thus, for purposesof the present invention, "substantially molecularly unoriented castfilms" are liquid cast films, and not melt cast films or films formed bymelt extrusion.

Colored pigments are uniformly distributed in the cast film bydispersing them in a vehicle compatible with the liquid from which thefilm is cast, and mixing the vehicle with the same prior to casting thefilm. When a metallic paint finish is desired, reflective flakepigments, such as aluminum flakes of the type used to produce metallicfinishes on automobiles, or mica flakes, either surface treated (e.g.,pigmented) or not, of the type used in automobile finishes, areuniformly distributed in the cast film in like manner. U.V. screenersare added as needed to improve the weatherability of the cast films. Forcertain automotive styling effects, the cast film 13 may be formed ofmultiple layers of liquid cast molecularly unoriented polymer. Forexample, the glossy wet look of a base coat/clear coat automotive finishis achieved by a combination of layers, with the outer or top layerbeing a transparent layer of high gloss and optical clarity, and with anunderlying opaque layer containing colored and/or metallic pigmentsproviding the desired color.

Polymers suitable for forming such weatherable cast films are selectedto provide a pigmented film which will not significantly fade, peel,chalk, or crack, when exposed to the environment, for the intended lifeof the product for which the molded plastic article is made. A number ofknown testing procedures, in which objects are exposed to either thenatural environment over an extended time or a harsh artificialenvironment for a short time, are used to determine the weatherabilityof polymers. Such weatherable polymers include fluoropolymers, acrylatepolymers, urethane polymers, and blends thereof. Acrylate polymersuseful for practicing the present invention are obtained from a varietyof acrylic monomers, such as acrylic and methacrylic acids, and theiramides, esters, salts, and corresponding nitriles. Particularly suitablemonomers for such polymers are methyl methacrylate, ethyl acrylate, andacrylonitrile. The polymers may each be used in the form ofhomopolymers, or with various other monomers which can be copolymerizedtherewith. Additional illustrative examples of acrylate polymers whichmay be useful for the present invention are thermoplastic polyacrylatesand polymethacrylates which are homopolymers and copolymers of acrylicacid ester and methacrylic acid ester, such as, for example, polyacrylicacid isobutyl ester, polymethacrylic acid methyl ester, polymethacrylicacid ethylhexyl ester, polyacrylic acid ethyl ester; copolymers ofvarious acrylic acid esters and/or methacrylic acid esters, such as, forexample, methacrylic acid methyl ester/acrylic acid cyclohexyl estercopolymers; and copolymers of acrylic acid esters and/or methacrylicacid esters with styrene and/or alpha-methylstyrene, as well as thegraft polymers and copolymers and polymer mixtures composed of acrylicesters, methacrylic acid esters, styrene and butadiene. A group oftransparent, weatherable blends of acrylate polymers and polyvinylidenefluoride polymers useful for practicing the present invention aredisclosed in U.S. Pat. No. 3,524,906. The disclosures of this patent,and all other patent references cited herein, are specifically intendedto be incorporated herein by reference.

Fluoropolymers useful for practicing the present invention includepolymers and copolymers formed from trifluoroethylene,tetrafluoroethylene, hexafluoropropylene, monochlorotrifluoroethyleneand dichlorodifluoroethylene. Copolymers and terpolymers of thesemonomers formed from fluoroolefins such as vinylidene fluoride are alsouseful. Further illustrative examples of fluoropolymers useful forpracticing the present invention include polyvinyl fluoride,polyvinylidene fluoride, fluorinated ethylene/propylene copolymers("FEP" resins), ethylene/chlorotrifluoroethylene copolymers, vinylidenefluoride/hexafluoropropene copolymers, and vinylidene fluoride/perfluoro(alkyl vinyl ether) dipolymers and terpolymers with tetrafluoroethylene.Illustrative of the commercially available fluoropolymer resins usefulfor practicing the present invention are those sold under suchtrademarks as KYNAR, FORAFLON, SOLEF, LUMIFLON, and TEFLON. These resinscan be formulated and formed by liquid casting into films. Anillustrative weatherable polymer film for use in the present inventionis an alloy of an acrylic polymer and polyvinylidene fluoride, such as"FLUOREX® (a trademark of Rexham Corporation).

Urethane polymers useful for practicing the present invention areprepared by reacting a polyisocyanate with a compound containing atleast two active hydrogen atoms, such as a polyol, a polyamine, or apolyisocyanate. Polyurethane resins for use in the present inventionshould be selected from resins in which the reactants have been chosento provide weatherable, thermoformable polymers. Numerous suitablepolyurethane resins useful for practicing the present invention areavailable. Generally, aromatic polyisocyanates tend to yellow, andaliphatic polyisocyanates are more preferred. Particularly noteworthyrecent developments in this area are disclosed in U.S. Pat. No.4,578,426 (disclosing resins which give coatings resistant to gasolineand having high flexibility, scratch resistance and weather resistance)and U.S. Pat. No. 4,501,852 (disclosing chemical resistant, abrasionresistant, elastic and durable polyurethanes).

The molded polymer substrate should be selected to provide engineeringproperties (rigidity, etc.) suited to the specific end use of theparticular article made. Such polymers are well known. Suitable polymersfor the molded polymer substrate include, for example, polyvinylchloride, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene,polyethylene, polypropylene, polyethylene terephthalate-glycol, nylon,and RIM urethanes. Polyolefin homopolymers and copolymers (ionomers,etc.) are inexpensive thermoplastic resins which have excellent moldingproperties and are particularly preferred for practicing the presentinvention. Polypropylene, for example, when glass filled and foamed witha blowing agent, has performance properties suitable for structural orengineering uses. Acid copolymers of polyethylene such as "SURLYN" (atrademark of E. I. DuPont De Nemours) are similar in performance and inaddition have exceptional toughness.

The bonding layer 14 of the decorative surfacing film 10 comprises athermoplastic polymer layer applied to the inner surface of the castpolymer film 13. In a preferred embodiment, the bonding layer 14comprises a preformed film of a thermoplastic polymer laminated to theinner surface of the cast film. Bonding of the decorative surfacing film10 to a polyolefin molded polymer substrate can be achieved with anintermediate bonding layer or layers in accordance with known laminatingprocedures, and with known adhesives. For example, a decorativesurfacing film formed of a cast polymer film layer which is bonded to orcoated with a fusible olefin bonding layer can be placed in a moldduring injection of an olefin resin. Another approach is to bond a PVCfilm to a cast weatherable fluoropolymer film with an acrylic adhesiveand, in turn, bond the PVC film to an olefin film with a polyesterisocyanate adhesive. The cast polymer film may also be laminated to anolefin film with a permanent type acrylic pressure-sensitive adhesive.

In addition to facilitating the bonding of the weatherable cast film tothe molded polymer substrate, the bonding layer 14 serves severaladditional important functions. Since the weatherable cast film hasrelatively little inherent tensile strength, the bonding layer serves asa reinforcement to facilitate handling of the decorative surfacing film,placement of the film into the mold, and also ensures that it remainswrinkle free in the mold during the molding operation. During molding,as molten plastic is injected into the mold cavity and flows to fill thecavity, the bonding layer acts as a protective stabilizing layer and asan insulator to maintain the high quality outer surface appearance ofthe surfacing film and prevent the injected molten plastic from causingheat distortion or flow lines which would be visible on the outersurface of the molded article. Thus, the decorative surfacing filmretains the gloss and distinctness of image properties which arecharacteristic of a high quality paint finish, such as the type of paintfinish used on an automobile. For shallow contoured parts, the surfacingfilm may be fed directly from the source roll into the mold cavity. Inproducing deep-drawn, highly contoured plastic articles, it is desirableto preform the decorative surfacing film, such as by vacuum forming,prior to placement in the mold. The thermoformability properties of thethermoplastic bonding layer make it possible for the surfacing film tobe vacuum thermoformed into a desired three-dimensional configuration,and insures that the thus pre-formed surfacing film retains itspre-formed shape during subsequent handling and placement in the mold ofthe injection molding machine.

The bonding layer 14 may be from about 0.25 to about 250 thousandths ofan inch thick, and most desirably a minimum thickness of 2 mils toensure good thermoformability and other properties as noted above.

Preferably, the tear strength of the cast film is less than the bondstrength of the cast film to the molded polymer substrate. This willprevent tears from forming in the cast film, running across the surfaceof the molded article, and quickly destroying the article. Instead, theweatherable cast polymer film surface will flake off in small particleswhen disrupted by nicks and scratches from stones and other flyingparticles, as routinely confronts automobile surfaces.

The cast weatherable film is preferably between 0.5 and 300 thousandthsof an inch thick, and most preferably from about one to about twothousandths of an inch thick. Similar molded parts can be achieved withinjected ABS and styrene by laminating the surface film to acorresponding substrate layer of ABS or styrene.

The present invention is carried out on conventional molding equipmentin accordance with known techniques. Particularly suitableinjection-molding equipment and techniques are disclosed in U.S. Pat.Nos. 4,397,806 and 4,307,057 to Hettinga. The decorative film may beheated and vacuum formed in a separate forming mold prior to beingplaced in the injection mold, or may be shaped by heat and pressure inthe injection mold.

The present invention is particularly suitable for making deep drawmolded articles. Deep draw articles, and deep draw molding procedures,are those in which the depth of the molded article is relatively largein relation to the length and width of the two dimensional decorativesurfacing film from which the article is made. More particularly, thedepth of the article should be such that substantial stretching andelongation of the decorative surfacing film occurs at least in regionsof the decorative surfacing film. Such substantial stretching andelongation occur when the decorative surfacing film is subjected toelongation of about 25% or more at least in regions thereof. The castfilm is preferably formed from a polymer selected so that the decorativesurfacing film will maintain a paint-like appearance, and will notstress whiten, when stretched and elongated.

With the surfacing film of the present invention, it is possible toproduce a structure formed from a set of assembled parts, wherein eachpart has a uniform decorative outer surface formed by a decorativesurfacing film. For example, a set of molded plastic automobile partscan be produced and assembled as shown in FIGS. 3 and 4. This methodcomprises the steps of first placing into a mold a preformed decorativesurfacing film of the type described above, then introducing a moldablepolymer into the mold as described above, and then molding the surfacingfilm and the polymer, as also described above. These three steps(placing the surfacing film into the mold; introducing polymer into themold; molding the surfacing film and the polymer) are then repeated foreach article in the set, so that each article in the set has the sameweatherable cast pigmented polymer film on the outer surface thereof. Asstated above, the articles in the set may or may not all be formed ofthe same moldable material. Therefore, for the making of each article,the decorative surfacing film has a bonding layer of a material whichhas been preselected to adhere to the particular moldable polymer fromwhich that particular article is made. While molding polymers may thusadvantageously differ from article to article, and bonding layers mayaccordingly differ from article to article, every article in the set hasthe same cast pigmented film on the outer surface thereof. As a result,when the set of molded articles is assembled into the aforesaidstructure, the need for spray-painting the structure to otherwiseprovide it with a uniform decorative outer surface is eliminated.

The present invention is explained further in the following nonlimitingexamples.

EXAMPLE 1

A weatherable cast film formed from an alloy of an acrylic polymer andpolyvinylidene fluoride (e.g., "FLUOREX"), is formed with internalpigments, including reflective metallic flakes. The film is laminated toa polyvinylchloride (PVC) film with an acrylic adhesive. Themultilayered film is then placed in a mold, the mold closed, and PVCinjected into the mold behind the polyvinylchloride bonding layer. ThePVC molding polymer and the weatherable film/PVC film laminate are thenmolded for a time and temperature sufficient to form a shaped article,with the weatherable film bonded to the outer surface thereof by the PVCbonding layer.

EXAMPLE 2

The procedure of Example 1 is repeated with polyethyleneterephthalate-glycol (PETG) as the bonding substrate and with PETG asthe molding polymer to form additional molded articles.

EXAMPLE 3

The same procedure is carried out as described in Example 1 above,except that the cast film is bonded to a PETG bonding film, and RIMurethane is used as the molding resin.

EXAMPLE 4

The same procedure is carried out as described in Example 1 above,except that the cast film is bonded to an acrylonitrile butadienestyrene (ABS) bonding film, and ABS is used as the injection-moldingpolymer.

EXAMPLE 5

A weatherable cast film formed from an alloy of an acrylic polymer andpolyvinylidene fluoride is bonded to a PVC film with an acrylicadhesive, and the PVC film is bonded to a polypropylene film bondinglayer with a polyester isocyanate adhesive. An .article is madeaccording to the procedures set forth in Example 1, with polypropyleneas the molding polymer. Other articles can be made with other olefins asbonding layers, and with thermoplastic olefins, known as "TPO polymers,"as molding polymers

EXAMPLE 6

A weatherable cast film formed from a fluoropolymer, an acrylatepolymer, a urethane polymer, or a blend thereof, is bonded, with anacrylate adhesive, to an ABS, PVC, or nylon film to form a decorativesurfacing film. Articles are made with such decorative surfacing filmsaccording to the procedures set forth in Example 1, with nylon moldingpolymers.

In the drawings and specification, there has been disclosed typicalpreferred embodiments of the invention. Although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the invention being set forthin the following claims.

That which is claimed is:
 1. A shaped article having a contoureddecorative outer surface, comprising a molded polymer substrate having acontoured three-dimensional outer surface and a preformed decorativesheet material adhered to and conforming to said contouredthree-dimensional outer surface, said decorative sheet material havingregions thereof which have been subjected to an elongation of about 25%or more, and said sheet material comprising a substantially molecularlyunoriented liquid-cast weatherable polymer film comprising an alloy of apolyvinylidene fluoride polymer and an acrylic polymer, and a bondinglayer formed of a thermoplastic polymer different from said cast polymerfilm, said bonding layer being adhered to the inner surface of said castpolymer film by an adhesive layer between said bonding layer and saidcast polymer film, and said bonding layer also being adhered to saidcontoured three-dimensional outer surface of said substrate, said castpolymer film having pigments therein providing color to the outersurface of said article, and said bonding layer comprising a polyolefinpolymer.
 2. A molded plastic article as claimed in claim 1, wherein saidbonding layer is formed from a thermoformable film having a thickness offrom about 0.2 to about 250 thousandths of an inch.
 3. A molded plasticarticle as claimed in claim 1, wherein said liquid cast film is between0.5 and 300 thousandths of an inch thick.
 4. A molded plastic articleaccording to claim 1 including an adhesive layer adhering said bondinglayer to said substrate.
 5. A molded plastic article according to claim1 wherein said cast polymer film has reflective metallic flakes therein.6. A molded plastic article according to claim 1 wherein said castpolymer film includes an outer transparent layer and an underlyingpigmented layer containing said pigments.
 7. A molded plastic articleaccording to claim 1 wherein said molded polymer substrate comprises apolyolefin polymer.